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Comparing Sizes of Microorganisms

Author(s): Nancy Moreno, PhD, Barbara Tharp, MS, Deanne Erdmann, MS, Sonia Rahmati Clayton, PhD, and James P. Denk, MA

Materials for Each Group of Students

To prepare for this experiment, use a word processing program to create a text document consisting of the following phrase, repeated on 24 individual lines: “The period at the end of this sentence is larger than a/an____.” 

NOTE: Be sure to use 12-point Helvetica font. Print the page, and cut it so that each row of text is an individual strip of paper. You also will need to prepare a 2.5-m  x  2.5-m square of paper, which will serve as a large scale model of the period at the end of the sentence.

Materials per student group

  • 4 prepared text strips
  • 4 hand lenses
  • 4 metric rulers with millimeters
  • 4 pairs of scissors
  • Assorted markers or colored pencils
  • Meter stick
  • Paper or a science notebook
  • Several sheets of colored or plain paper, or roll of chart or craft paper
  • Tape or glue
  • Copy of “Microbe Scaling Chart” student sheet
  • Group concept map (ongoing)


Have students work in groups of four.

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Funded by the following grant(s)

Science Education Partnership Award, NIH

Science Education Partnership Award, NIH

Grant Number: 5R25RR018605